POLLUTED SHELL-FISH 423 



could not be isolated from 100 c.c. of the infected water, 

 indicating that the uncultured bacillus rapidly dies in a 

 natural water, and that even a week's storage of water 

 affords enormous protection against water-borne typhoid. 

 In aerated (C0 2 ) waters the B. lyphosus does not survive a 

 fortnight. The methods of isolation from water are given 

 in Chapter XXI. 



The Bacillus lyphosus may gain access to shell-fish, 1 

 oysters, mussels, cockles, etc., particularly if obtained 

 from sewage-polluted laying. Such polluted shell-fish 

 may give rise to typhoid epidemics as at Winchester 

 and Southampton in the case of oysters, or to sporadic 

 cases, as occurs with cockles derived from the Thames 

 Estuary and imperfectly cooked. Buchan found that out 

 of 855 primary cases of typhoid fever occurring in house- 

 holds in Birmingham, 124, or 14-5 per cent., had a history 

 of mussel eating, and in seventeen instances the histories 

 were conclusive of mussel infection. Shell-fish from 

 sewage-polluted layings contain B. coli in varying num- 

 bers, but from uncontaminated layings are free from this 

 organism, which may therefore serve as an index of pollu- 

 tion (see " Examination of Shell-Fish," Chapter XXI). 

 Contaminated shell-fish, removed to pure water, gradually 

 cleanse themselves probably after two to three weeks' 

 sojourn. Klein obtained the typhoid bacillus from 

 artificially infected oysters, kept in tanks of sea-water, 

 after nine, sixteen, and even eighteen days from the 

 commencement of the experiment, the oysters showing no 

 abnormal condition. 



As regards the vitality of the Bacillus typliosus in sewage 



1 On pathogenic organisms in shell-fish see Reports by Bulstrode to the 

 Local Government Board, 1894 and 1911 ; Rep. Med. Off. Loc. Gov. Board 

 for 1899-1900, p. 574 ; Houston, Fourth Report of the Sewage Commission, 

 vol. iii, 1904 ; McWeeney, Loc. Gov. Board, Ireland, 1904 ; Buchan, Journ. of 

 Hygiene, vol. x, 1910, p. 569. 



